We do not find any evidence of \(^{15}\) N isotopic fractionation. Towards L1157-mm, we obtain \(^{13}\) C/\(^{15}\) N ratios of \(5.8\pm 2.2\)  and \(4.8\pm 2.4\)  for HCN and HNC, respectively. Both values agree within the uncertainties, and they are also consistent with the canonical elemental abundance ratio of 6.5 in the local ISM [1]}, [2]}. This translates into elemental abundance ratios HC\(^{14}\) N/HC\(^{15}\) N of \(380\pm 145\)  and H\(^{14}\) NC/H\(^{15}\) NC \(\approx 320\pm 160\)  towards L1157-mm. Both values are consistent with the solar value in the local ISM (440; [2]}). Towards L1157-B1, the H\(^{13}\) CN/HC\(^{15}\) N is almost unchanged (\(5.0\pm 2.5\) ) whereas the HN\(^{13}\) C/H\(^{15}\) NC takes a lower value (\(3.0\pm 1.5\) ), but still in rough agreement with the canonical value.
